1. Field of the Invention
The present invention relates to a developing cartridge in which a toner storage unit (toner cartridge) is removably mounted in a main unit and to an image forming apparatus in which the developing cartridge is removably mounted.
2. Description of the Related Art
Conventionally, in an image forming apparatus (electrophotographic image forming apparatus) that uses the electrophotographic image forming process, cartridge systems have been used to allow the process unit in the apparatus main body of the image forming apparatus (apparatus main body) to be replaced as one unit.
One cartridge system is a developing cartridge in which a developing device, such as a developing roller, is provided in the cartridge. Another cartridge system is a process cartridge in which the electrophotographic photosensitive drum and the process unit, which acts on the electrophotographic photosensitive drum, are integrated into a cartridge as one unit. A process cartridge may also be provided with a photosensitive member in a developing cartridge having a developing roller that works as the process unit.
Still another cartridge system is a toner cartridge system that is removably provided, with a toner storage unit that stores toner, in a developing cartridge. The toner cartridge system allows the user to replace the toner storage unit independently of the other parts that configure the developing cartridge such as the photosensitive drum and developing roller.
Therefore, the toner cartridge system is advantageous when the consumption cycle of toner stored in the toner storage unit differs from the product lifetime of the other parts configuring the developing cartridge such as a photosensitive drum and a developing roller.
According to the image forming apparatus discussed in Japanese Patent Application Laid-Open No. 2004-333929, a user who wants to replace the toner cartridge opens a door of the image forming apparatus provided for replacing toner cartridge and replaces the toner cartridge. This configuration allows the user to replace the toner cartridge without having to take the main unit of the developing cartridge out of the image forming apparatus.
The image forming apparatus in the above-described art requires that the door for replacing the toner storage unit is separate from the door for replacing the main unit of the developing cartridge. Therefore, when the image forming apparatus in the art is compared with an image forming apparatus where the same door is used for replacing both the main unit of the developing cartridge and the toner storage unit, several differences becomes apparent.
The use of multiple doors requires an increase in the number of parts for the image forming apparatus. More specifically, additional doors result in an increase in door bodies, hinge axes of the doors, and door handles. The use of multiple doors also results in a decrease in the strength of the main body of the image forming apparatus. That is, the more holes bored on the side-plate of the image forming apparatus for providing door openings, the weaker the strength of the side-plate becomes.